1. Field of the Invention
The present invention relates to an inkjet printer head.
2. Discussion of Related Art
There is known an inkjet printer head including: a head unit having an ink inlet, a multiplicity of pressure chambers and a multiplicity of nozzles; an ink supply passage communicating an ink source and the ink inlet so as to supply an ink from the ink source to the ink inlet; and a piezoelectric actuator plate mounted on the head unit and operable to pressurize the ink stored in a selected one or ones of the pressure chambers so that the ink is ejected through a corresponding one or ones of the nozzles which are held in communication with the selected pressure chamber or chambers.
To the ink inlet of the head unit, there is connected a resin member defining an ink channel which is held in communication with the ink supply passage, so that the ink can be supplied into the head unit from the ink source via the ink channel defined by the resin member. There is an arrangement in which a plurality of ink inlets are provided in the head unit, for distributing the ink into a plurality of portions of a nozzle plate which is provided by a lower portion of the head unit, so that the ink can be ejected evenly from the multiplicity of nozzles which are formed through the nozzle plate. In this arrangement, a plurality of branch channels are interposed between the single ink channel and the plurality of ink inlets, so that the ink is supplied from the ink source to each of the plurality of ink inlets via the single ink channel and a corresponding one of the branch channels.
It is common that the single ink channel communicated with the ink source via the ink supply passage is forked or divided into two branch channels as the plurality of branch channels.
JP-2003-220705A discloses an inkjet printer head unit in which an ink channel is divided into two branch channels at a fork that is surrounded by a circumferential wall. The circumferential wall is tapered such that a diameter defined by the circumferential wall is increased as viewed in a direction of flow of an ink supplied from an ink source (see FIG. 11 of JP-2003-220705A), for restraining an air from being accumulated in the fork or the branch channels.
In the arrangement in which the ink channel communicated with the ink source via the ink supply passage is simply divided into the two branch channels, the ink could flow into only one of the two branch channels, rather than into both of the two branch channels. In such an event, however, this state is maintained without the ink being forced to flow into the other branch channel, so that the ink cannot be distributed evenly into the two branch channels.
The provision of the tapered circumferential wall surrounding the fork is effective merely to provide a large ink passage so as to stabilize the flow of the ink therethrough, but does not serve to recover even distribution of the ink into the two branch channels.